Experts are concerned that Mycoplasma genitalium (MG), which is spread by sex as well as sexual touching or rubbing, is becoming resistant to antibiotics.
A large study from 2015 found that one in 100 UK adults aged 16 to 44 were infected with MG, with the majority showing no symptoms.
Elsewhere, a more recent study in Australia estimated that up to 2 per cent of Australians carry MG, according to 9 News.
Professor Suzanne Garland, from Melbourne's Royal Women's Hospital, told abc.net.au that people who were infected with the bug often had no symptoms. Some men will have pain when urinating, while some women report pain during sex or when urinating.
Young, sexually active men and women with different partners are at risk.
She is concerned that treatment with antibiotics may be becoming increasingly limited:
It's essentially acting like a superbug, with research showing at least 50 per cent of people have a drug-resistant MG, limiting their treatment options.